Node.js util.types.isWeakMap() Method

Last Updated : 13 Oct, 2021
The util.types.isWeakMap() method is an inbuilt application programming interface of util module which is primarily designed to support the needs of Node.js own internal APIs. The util.types.isWeakMap() method is used to determine whether the value is a built-in WeakMap instance or not. Syntax: 
util.types.isWeakMap( value )
Parameters: This method accepts a single parameter value which holds any valid JavaScript data types like Boolean, Null, Number, Object, etc. Return value: It returns a Boolean value i.e. returns true if it is an instance of built-in WeakMap, otherwise it returns false. Below examples illustrate the use of util.types.isWeakMap() method in Node.js: Example 1: javascript 
// Node.js program to demonstrate the 
// util.types.isWeakMap() method 

// Using require to access util module 
const util = require('util');

// Using util.types.isWeakMap() method
console.log(util.types.isWeakMap(true));

// Using util.types.isWeakMap() method
console.log(util.types.isWeakMap("map"));

// Using util.types.isWeakMap() method
console.log(util.types.isWeakMap(new WeakMap()));
Output: 
false
false
true
Example 2: javascript 
// Node.js program to demonstrate the 
// util.types.isWeakMap() method 
 
// Using require to access util module 
const util = require('util');
 
// Creating a Boolean Object
const a = new Boolean(true);
 
// Creating a Boolean Object
const b = new Boolean(false);
 
// A boolean type variable
const c = new WeakMap();
 
// Using util.types.isWeakMap() method
console.log(util.types.isWeakMap(a));
 
// Using util.types.isWeakMap() method
console.log(util.types.isWeakMap(b));
 
// Using util.types.isWeakMap() method
console.log(util.types.isWeakMap(c));
Output: 
false
false
true
Note: The above program will compile and run by using the node index.js command. Reference: https://nodejs.org/dist/latest-v13.x/docs/api/util.html#util_util_types_isweakmap_value
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